Neuromotor disorders such as spinal cord injury (SCI) and stroke lead to distinct impairments of motor pattern generation and balance (Courtine, G., et al. Transformation of non-functional spinal circuits into functional states after the loss of brain input. Nat Neurosci 12, 1333-1342 (2009); Harkema, S. J., et al. Human lumbosacral spinal cord interprets loading during stepping. J Neurophysiol 77, 797-811 (1997).)
Consequently, dissociating these sub-functions is essential for assessment and neurorehabilitation of gait. Conceptually, neurorehabilitation systems should act as a propulsive or postural neuroprosthesis that assist or perturb propulsion, balance, or the combination of both to varying degrees according to experimental purposes or patient-specific needs.
Existing systems used to compensate for impaired propulsion and balance rely on passive spring support, counterweight mechanisms, or closed-loop force control systems that generate vertical forces at the trunk level during treadmill-restricted stepping (Nessler, J. A., et al. A robotic device for studying rodent locomotion after spinal cord injury. IEEE transactions on neural systems and rehabilitation engineering: a publication of the IEEE Engineering in Medicine and Biology Society 13, 497-506 (2005); Frey, M., et al. A novel mechatronic body weight support system. IEEE transactions on neural systems and rehabilitation engineering: a publication of the IEEE Engineering in Medicine and Biology Society 14, 311-321 (2006)). However, these approaches present several drawbacks: (i) current systems only provide support in the vertical direction whereas well-balanced locomotion requires finely tuned trunk movements in virtually every direction (Winter, D. A., MacKinnon, C. D., Ruder, G. K. & Wieman, C. An integrated EMG/biomechanical model of upper body balance and posture during human gait. Prog Brain Res 97, 359-367 (1993)); (ii) the optic flow, which significantly modulates locomotion (Orlovsky, G. N., Deliagina, T. G. & Grillner, S. Neuronal control of locomotion: from mollusc to man, (Oxford University Press, Oxford, 1999)), is suppressed during treadmill-restricted stepping; (iii) rehabilitation is restricted to stepping on a treadmill (Musselman, K., Brunton, K., Lam, T. & Yang, J. Spinal cord injury functional ambulation profile: a new measure of walking ability. Neurorehabilitation and neural repair 25, 285-293 (2011)); a condition that markedly differs from the rich repertoire of natural locomotor tasks.
Robotic systems have been designed to overcome these limitations. The ZeroG (Hidler, J., et al. ZeroG: overground gait and balance training system. Journal of rehabilitation research and development 48, 287-298 (2011)) provides vertical support during overground walking using a lifting unit mounted on a rail-guided trolley. However, the rails constrain subjects along a fixed direction, and trunk support is restricted to the vertical direction. The NaviGaitor (Shetty, D., Fast, A. & Campana, C. A. Ambulatory suspension and rehabilitation apparatus (U.S. Pat. No. 7,462,138)) allows translations in all directions by means of an overhead linear multi-axis system, but its massive structure leads to high inertia that prevents normal-paced movements.
Therefore, there is the problem to have a robotic system which overcomes the drawbacks of the prior art. In particular, there is the need of a multidirectional trunk support system that solves these various issues. Another problem in the art is that the evaluation of locomotor function in subjects often relies on visual scoring systems (Basso, D. M., et al. MASCIS evaluation of open field locomotor scores: effects of experience and teamwork on reliability. Multicenter Animal Spinal Cord Injury Study. Journal of neurotrauma 13, 343-359 (1996)) or single-variable analysis (Zorner, B., et al. Profiling locomotor recovery: comprehensive quantification of impairments after CNS damage in rodents. Nature methods 7, 701-708 (2010)) that not only lack objectivity but also fail to capture the multidimensional correlative structures of locomotor control strategies (Musienko, P., et al. Controlling specific locomotor behaviors through multidimensional monoaminergic modulation of spinal circuitries. J Neurosci 31, 9264-9278 (2011)).
It is well-known that activity-based interventions exploiting proprioceptive information to enhance spinal motor output during training (H. Barbeau, S. Rossignol, Recovery of locomotion after chronic spinalization in the adult cat. Brain Res 412, 84 (May 26, 1987); R. G. Lovely, R. J. Gregor, R. R. Roy, V. R. Edgerton, Effects of training on the recovery of full-weight-bearing stepping in the adult spinal cat. Experimental neurology 92, 421 (May, 1986); A. Wernig, S. Muller, Laufband locomotion with body weight support improved walking in persons with severe spinal cord injuries. Paraplegia 30, 229 (April 1992)) promote plastic changes capable of restoring locomotion after severe though incomplete spinal cord injury (SCI) (A. Wernig, S. Muller, Laufband locomotion with body weight support improved walking in persons with severe spinal cord injuries. Paraplegia 30, 229 (April 1992); A. Wernig, S. Muller, A. Nanassy, E. Cagol, Laufband therapy based on ‘rules of spinal locomotion’ is effective in spinal cord injured persons. Eur J Neurosci 7, 823 (Apr. 1, 1995)).
A recent case study suggests that, in combination with epidural electrical stimulation of lumbosacral segments, activity-based rehabilitation may also restore supraspinally-mediated movements after motor complete paraplegia (Harkema, S., et al. Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study Lancet, 377, 1938 (Jun. 4, 2011)).
There is a mosaic of evidence suggesting that gait rehabilitation should be conducted overground (Wessels, M., Lucas, C., Eriks, I. & de Groot, S. Body weight-supported gait training for restoration of walking in people with an incomplete spinal cord injury: a systematic review. Journal of rehabilitation medicine: official journal of the UEMS European Board of Physical and Rehabilitation Medicine 42, 513-519 (2010)), across multiple walking paradigms (Musselman, K., Brunton, K., Lam, T. & Yang, J. Spinal cord injury functional ambulation profile: a new measure of walking ability. Neurorehabilitation and neural repair 25, 285-293 (2011)), with adequate support conditions (Wessels, M., Lucas, C., Eriks, I. & de Groot, S. Body weight-supported gait training for restoration of walking in people with an incomplete spinal cord injury: a systematic review. Journal of rehabilitation medicine: official journal of the UEMS European Board of Physical and Rehabilitation Medicine 42, 513-519 (2010); Reinkensmeyer, D. J., et al. Tools for understanding and optimizing robotic gait training. Journal of rehabilitation research and development 43, 657-670 (2006); Ada, L., Dean, C. M., Vargas, J. & Ennis, S. Mechanically assisted walking with body weight support results in more independent walking than assisted overground walking in non-ambulatory patients early after stroke: a systematic review. Journal of physiotherapy 56, 153-161 (2010)), enabling systems (Courtine, G., et al. Transformation of nonfunctional spinal circuits into functional states after the loss of brain input. Nat Neurosci 12, 1333-1342 (2009); Harkema, S., et al. Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study. Lancet 377, 1938-1947 (2011); Kwakkel, G., Kollen, B. J. & Krebs, H. I. Effects of robot-assisted therapy on upper limb recovery after stroke: a systematic review. Neurorehabilitation and neural repair 22, 111-121 (2008); Edgerton, V. R. & Roy, R. R. Robotic training and spinal cord plasticity. Brain research bulletin 78, 4-12 (2009); Reinkensmeyer, D. J., et al. Tools for understanding and optimizing robotic gait training. Journal of rehabilitation research and development 43, 657-670 (2006)), task-specific sensory cues (Courtine, G., et al. Transformation of nonfunctional spinal circuits into functional states after the loss of brain input. Nat Neurosci 12, 1333-1342 (2009); Harkema, S., et al. Effect of epidural stimulation of the lumbosacral spinal cord on voluntary movement, standing, and assisted stepping after motor complete paraplegia: a case study. Lancet 377, 1938-1947 (2011)), and active patient cooperation (Duschau-Wicke, A., Caprez, A. & Riener, R. Patient-cooperative control increases active participation of individuals with SCI during robot-aided gait training. Journal of neuroengineering and rehabilitation 7, 43 (2010); Edgerton, V. R. & Roy, R. R. Robotic training and spinal cord plasticity. Brain research bulletin 78, 4-12 (2009)), but these concepts remain fragmented and there is no indication on how to arrive at a unified therapeutic tool to evaluate and restore locomotor function after CNS disorders, both in animals and in humans.
Moreover, according to the state of the art, voluntary control of movement still cannot be achieved by the subject.
There is still the problem to provide a method for rehabilitation of a subject suffering from neuromuscular disturbance, in particular partial or total paralysis of limbs, this method achieving voluntary control of movement.
There is also the need to provide an apparatus for restoring voluntary control of locomotion in a neuromotor impairment which is capable of acting as a propulsive or postural neuroprosthesis that assists or perturbs propulsion, balance, or the combination of both to varying degrees according to experimental purposes or patient-specific needs. In particular, this apparatus should be capable of performing an objective evaluation of locomotor functions, capturing the multidimensional correlative structures of locomotion functions. Further, such an apparatus should be able to guide the subject in need of restoring voluntary control of locomotion and also to be “transparent” to the subject, as the case may be.